It reminds them of an experience they might want to forget. Further, it requires them to deal with a topic they may be completely sick and tired of.
From the comment above me (emphasis mine):
Apologies communicate knowledge of harmful behavior, ideally in a way that lets the victim understand and get closure on the incident. They help in reducing attribution bias (where people assume you’re a jerk, rather than a fallible human).
I’ll note that this means that an apology can turn an experience one wants to forget into a completely tolerable one. If someone shows up late to a bunch of meetings and acts disrespectful while they’re there, I’ll be annoyed at them and find our interactions unpleasant in the future, even if don’t act out anymore. But if they then say “Sorry about last week, I was having a rough time and I let my emotions get the best of me. I’m not going to act like that in the future” then the experience of “this person was a jerk, which I find unpleasant” is retroactively transformed into “this person was going through something, which happens to all of us”
From the post:
From the comment above me (emphasis mine):
I’ll note that this means that an apology can turn an experience one wants to forget into a completely tolerable one. If someone shows up late to a bunch of meetings and acts disrespectful while they’re there, I’ll be annoyed at them and find our interactions unpleasant in the future, even if don’t act out anymore. But if they then say “Sorry about last week, I was having a rough time and I let my emotions get the best of me. I’m not going to act like that in the future” then the experience of “this person was a jerk, which I find unpleasant” is retroactively transformed into “this person was going through something, which happens to all of us”